Process for the production of beryllium having increased ductility at high temperatures



il'nited States Patent @fifice 3,065,117 Patented Nov. 20, 1952 PROCESS FQR THE PRODUCTION OF BERYLLIUM HAVING INCREASED DUCTILITY AT HIGH TEMPERATURES Alexander Baillie Brown, Kilmarnock, Scotland, and Alfred John Martin, Newbury, and Frederick Morrow, Todley, England, assignors to Babcock and Wilcox Limited, London, England Filed Aug. 17, 1960, Ser. No. 50,135 Claims priority, application Great Britain Aug. 29, 1959 Claims. (Cl. 148-43) The invention relates to the production of beryllium having increased ductility at high temperatures.

The metal beryllium has properties which could make it of considerable use in a wide number of fields. In particular it has a low neutron capture cross-section and is therefore of considerable interest in the nuclear field. Under some conditions it is, however, very brittle and difiicult to fabricate. Beryllium has low ductility at low temperatures. The ductility increases as the temperature rises reaching a maximum in the region of 300 C. to 400 C. after which it decreases. At temperatures in the region of 700 C. it may increase again, but not significantly.

The present invention provides a process for the production of beryllium having increased high temperature duetilit' in particular having increased ductility between about 300 C. and about 700 C.

The present invention provides a process for the production of beryllium having increased high temperature ductility in which thermally reduced beryllium or like equivalent beryllium is heated to a temperature above 600 C., held at a temperature within the range of 600 and 850 C. for a suitable period of time and then cooled to room temperature.

The effect of the process is different from that of annealing since after the stresses in the metal have been relieved a continuing increase in ductility is obtained as the metal is held at the temperature of treatment.

Another difference between an annealing process and that of the invention is that while annealing may be applied in general to beryllium the process of the invention can be applied successfully only to some beryllium namely to beryllium of the nature produced by thermal reduction. Thus, while the process is applicable to thermally reduced beryllium, it is inefiective when applied to beryllium produced by the electrolytic process. Whether a sample of beryllium is a like equivalent to thermally reduced beryllium in that the process of the invention can be successfully applied is a matter which may be determined by test.

The reason for the increase in ductility in beryllium heat-treated in accordance with the process of the invention is not clearly known but it is considered that it is probably due to precipitation of impurities and that iron and at least one other impurity possibly aluminum are involved. In this connection it is to be noted that the iron-content of beryllium as produced by the reduction of BeF by Mg is typically of the order of 1000 ppm. or 0.1%, while the iron content of beryllium produced by the electrolysis of a BeCI -NaCI melt is typically of the order of only 200-400 p.p.m. Whatever the reason, whether or not a sample of beryllium is for the purpose of this invention beryllium of the nature produced by thermal reduction is ascertainable by the means of a simple test.

The degree of high-temperature ductility obtained depends upon the time and temperature employed in the heat treatment. Heating for at least 12 hours produces a marked result at all temperatures at which the beryllium is held Within the range. The time taken in any instance to attain a particular degree of ductility depends upon the temperature which is preferably at least 700 and more preferably in the range between 750 C. and 850 C. While a shorter time may sufiice it may be found advantageous to heat for at least 24 hours and even for more than 72 hours. Thus at a temperature of 600 C. the beryllium may be heated with advantage for several weeks.

The heat treatment is carried out in an atmosphere inert to beryllium, e.g. argon or vacuum, in any suitable furnace. After the heat treatment the beryllium is cooled slowly in any manner convenient. It has been found convenient to cool the beryllium in the same environment as that in which the heat treatment was carried out.

The process of the present invention is illustrated in the following example.

EXAMPLE Thermally reduced beryllium, having the analysis shown in Table I, was heat treated at 780 C. for 120 hours and cooled to room temperature over 120 hours.

Table 1 Average of 3 analyses,

Alloy: ppm. in weight Iron 993 Aluminum 663 Silicon 843 Magnesium 9 Manganese Nickel 220 Copper 10 Chromium Oxygen 240 Beryllium carbide 400 Beryllium Remainder The figure shows the variation of elongation at varying temperatures of beryllium having the analysis shown in Table I, extruded at 1050 C. and tested at this stage, compared with the same material, which, after extrusion, has been heat treated in accordance with the invention. The extruded beryllium, which has now been subjected to the process of the present invention, shows a maximum ductility at about 200 C. after which the ductility falls slightly to about 300 C. and then more sharply to about 600 C. The same material, heat treated after extrusion, in accordance with the invention, shows a progressively increasing ductility up to 700 C.

It is considered that the increased ductility after heat treatment according to the present invention would be of particular benefit in the fabrication of beryllium at temperatures above 400 C. and in any high temperature use of beryllium where high creep or tensile ductility is required.

We claim:

1. A process for the production of beryllium having materially increased ductility on the order of at least about 25% in the temperature range 300-700 C. from beryllium reduced by thermal reduction, which comprises heating the thermally reduced beryllium to a temperature 3 above 600 C., maintaining the temperature within the range of about 600850 C. for a period of time at least about 5 hours, and permitting the treated beryllium to cool to room temperature.

2. A process in accordance with claim 1, wherein the temperature is maintained within the selected temperature range for a period of time of at least about 12 hours.

3. A process in accordance with claim 1, wherein the temperature is maintained within the selected temperature range for a period of time of at least about 24 hours.

4. A process in accordance with claim 1, wherein the temperature is maintained Within the selected temperature range for a period of time of at least about 72 hours.

5. A process in accordance with claim 1, wherein the temperature to which the beryllium is heated and that at which it is maintained is at least about 700 C.

6. A process in accordance with claim 1, wherein the heat treatment is carried out in an atmosphere inert to beryllium.

References Cited in the file of this patent Transactions of the A.S.M., vol. 42, pp. 816-827, 1950. Transactions of the A.S.M., vol. 42, pp. 785793, 828, 42, 1950. 

1. A PROCESS FOR THE PRODUCTION OF BERYLLIUM HAVING MATERIALLY INCREASED DUCTILITY ON THE ORDER OF AT LEAST ABOUT 25% IN THE TEMPERATURE RANGE 300-700*C. FROM BERYLLIUM REDUCED BY THERMAL REDUCTION, WHICH COMPRISES HEATING THE THERMALLY REDUCED BERYLLIUM TO A TEMPERATURE ABOVE 600*C., MAINTAINING THE TEMPERATURE WITHIN THE RANGE OF ABOUT 600-850*C. FOR A PERIOD OF TIME AT LEAST ABOUT 5 HOURS, AND PERMITTING THE TREATED BERYLLIUM TO COOL TO ROOM TEMPERATURE. 